1. Field of the Invention
The invention relates to a holding device for assembling a medical device, of the type used to take samples of bodily fluids, such as blood, urine, etc., and also for removing samples from containers needed for administering serum, plasma or medical substances.
2. The Prior Art
A holding device for a blood sample tube of a blood sample device is well known from patent specification U.S. Pat. No. 5,897,508 A, for example, which has a receiving vessel for a front end of the blood sample tube, sealed by a closure device, incorporating a needle holder. A cannula is mounted in the needle holder, directed towards the open front end of the receiving vessel, and projects in the direction thereof. A through-flow opening communicates via a connecting passage disposed between the needle holder and an end wall of the receiving vessel, with a sample needle of a needle assembly, disposed eccentrically with respect to a central longitudinal axis of the receiving chamber. Disposed between the connecting passage and a receiving chamber of the receiving vessel is a valve arrangement which can be opened as and when necessary. This valve arrangement incorporates a hose valve or flap valve disposed between the cannula and the receiving chamber and/or connecting passage. The cannula is preferably disposed concentrically with the receiving vessel. A through-flow passage opens between the cannula and an outer wall of the receiving vessel into the connecting passage. The disc-shaped support part has a periphery with an annular collar projecting out therefrom towards the end wall of the receiving vessel and the collar has an end surface connected to a peripheral bearing surface of the front wall of the receiving vessel in a gas-tight and liquid-proof manner by means of a continuous weld seam.
Other holding devices for blood sample tubes of a blood sample device are known from patent specification WO 89/10723 A1, for example, which has a receiving vessel for a front end of the blood sample tube. The blood sample tube is closed at its front end by a closure device. The receiving vessel is provided with a needle holder for a cannula and projects in the direction of an open front end of the receiving vessel, the through-opening of which is connected to a sample needle of a needle assembly via a connecting passage disposed between the needle holder and the end wall of the receiving vessel. This sample needle is disposed eccentrically with respect to a central longitudinal axis of the receiving chamber. Between the connecting passage and a receiving chamber of the receiving vessel, a valve arrangement is provided which can be opened as and when required. This valve arrangement comprises the cannula and the needle holder. The cannula is mounted so as to be adjustable in the lengthways direction of the central longitudinal axis of the receiving vessel in a bore of the needle holder. To restrict the adjusting movement, the cannula has a stop projecting out in a radial direction from the outer periphery at its end disposed in the connecting passage. This being the case, the cannula is squeezed together at its end facing the connecting passage and is bent around through 90 degrees and has an opening in the side wall through which the through-flow opening establishes a flow communication with the connecting passage. A disadvantage of this arrangement is the fact that the cannula is displaceably mounted in the needle holder, which makes it difficult to achieve a gas-tight seal between the sample needle and the blood sample tube, and in addition to permeability, which to a certain extent also leads to some leakage of blood, the vacuum of the blood sample tube can not be deployed for taking the blood sample in many cases.
Other blood sample devices are known from U.S. Pat. No. 4,819,659 A, European applications 0 478 459 A1, 0 286 087 A2 and 0 364 777 A1, in which the cannula in each case is of a continuous design and is mounted in a needle holder or in a guide sleeve. This being the case, the cannula simultaneously constitutes the sample needle at one end and the needle used to puncture the closure plug of the blood sample tube at the other end. In addition, at the end facing the blood sample tube, the cannula is surrounded by a valve arrangement in the form of a hose valve, which can be opened as and when required. In these embodiments of the sample device, it is not possible to separate the holding device from the needle assembly, for example in order to be able to administer an infusion to the patient, without having to remove the needle. Furthermore, an increased safety risk exists for the user because the sample needle is already fixed and injuries can already occur during preparation of the holding device. Another disadvantage is the fact that the sample needle, which is of a continuous design, is disposed centrally with respect to the holding device, as a result of which the entire sample device has to be inclined to a greater degree when piercing the vein, thereby increasing the risk of injury.